Jonno said:
How many amps can your battery output?
Is it as simple as 4000 watts divided by 72 volts equals 55 amps assuming the battery output is capable of 55amps without breaking a sweat and the controller is rated at no more than 55 amps output.
Just because the motor is rated at 4000 watts doesn't mean it should be taxed at 4000 watts OR does it if there's a built-in safety factor above 4000 watts ?
If controller is no more than 55 amp rating then a BT programmable BMS rated at least 75 amps should provide sufficient buffer.